System for enhanced detection of a target

ABSTRACT

Disclosed herein is a computer-readable medium having stored thereon computer-executable instructions for providing phase-range data associated with a return pulse of a radar device and second phase-range data associated with a successive return pulse of the radar device. The computer-executable instructions are preferably also for comparing the phase-range data and the second phase-range data to obtain a difference, and for differentiating the difference. In some embodiments of the invention, the computer-executable instructions are preferably also for discriminating a target from clutter by using the differentiated difference to identify coordinates satisfying a velocity threshold associated with the clutter. Embodiments of the invention preferably enable phase-coherent operation of a non-coherent radar device by processing backscattered clutter return, and in some aspects, do so using clutter distributed in range as a reference. Related systems, methods, devices, and other embodiments are also disclosed herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

The current application claims the benefit under 35 U.S.C. § 119(e) ofU.S. provisional patent application 60/607,122 filed on Sep. 3, 2004,which is hereby incorporated by reference in its entirety for allpurposes.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention disclosed herein relates generally to a system, method anddevice for enhanced detection of a target. More specifically, preferredembodiments of the disclosed invention relate to an enhanced detectionsystem, method and device to discriminate a target from clutter using anexisting non-coherent radar device.

2. Description of the Related Art

Known magnetron-based radar devices use the amplitude informationassociated with an echo or return pulse in an attempt to detect atarget. While amplitude-based detection is suitable for somecircumstance, it is not preferable for all circumstances particularlywhen the target is small, when there is a large amount of clutterrelative to the target strength, or both.

Phase-based detection generally provides enhanced levels of targetdetection allowing for easier recognition of a target from surroundingclutter. The prior art includes phase-based detection radar systems,referred to as coherent radar systems (and include coherent-on-receivesystems), which provide enhanced levels of target detection based on thephase information associated with the return pulse. However, thecoherence of these prior art systems is largely attributable to hardwaretechniques in which the received phase is directly or indirectly relatedto the phase of the transmitter or some other host-radar reference. Thecost of many of these coherent radar systems can range from four toeight million dollars, while the cost of non-coherent magnetron-basedradar system can run as little as five thousand dollars. The magnitudeof the cost differential is due, at least in part, to the use of costlytransmitter/receiver technologies that are used to obtain phasecoherence. There is a need for a low-cost alternative to achievingcoherence that provides enhanced target detection.

Prior art embodiments of coherent radar devices include, for example,fully-coherent radar devices and coherent-on-receive radar devices.Known embodiments of fully-coherent radar device include transmit andreceive oscillators that are in a fixed-phase relationship with oneanother. The transmitter and receiver of these embodiments either sharean oscillator or use two separate oscillators locked to the same source.By contrast, known embodiments of coherent-on-receive devices use asubstantially stable reference oscillator to correct phase differencesat the receiver, based on phase differences from the transmitter.Fully-coherent radar devices and coherent-on-receive devices are bothexamples of a coherent radar device.

Known techniques used to achieve coherence of a simple, magnetron-based,non-coherent radar device require that the hardware of the radar devicebe modified. Invasive hardware modifications, including the addition ofcomponents and signal paths, may be cost-prohibitive. There are no knownexamples of a system for non-invasive modifications that providecoherence of return pulses received by a non-coherent radar device.However, there is a need for a device that can be coupled to amagnetron-based or other non-coherent radar device to enhance detectionof a target and techniques for achieving coherence. Overcoming thedisadvantages present in the prior art, various embodiments of theinvention comprise a system, device and/or method for cohering theintermediate frequency signal of a radar device for enhancing levels oftarget detection.

SUMMARY OF THE INVENTION

Preferred embodiments of the enhanced detection device include a mixer,a coherent oscillator, an analog-to-digital (A/D) converter, a digitalsignal processor (DSP), a central processing unit (CPU) and a display.Preferred embodiments of the enhanced detection device also include aninput device for controlling the central processing unit, digital signalprocessor and/or other components. The enhanced detection device may becoupled to an existing radar device and, in some embodiments, theenhanced detection device may itself comprise an integrated radardevice.

The mixer is for receiving an intermediate frequency (IF) signal in ananalog format from the radar device. The intermediate frequency signalcontains information obtained from the return pulse received from atarget. The intermediate frequency signal often further includes signalcomponents associated with clutter and/or noise. The coherent oscillatorpreferably generates a coherent signal, which is then mixed with theintermediate frequency signal at the mixer. The mixer preferably sendsan in-phase (I) signal and a quadrature (Q) signal in an analog formatto the analog-to-digital converter for conversion of the analog formatinto digital format.

The digital signal processor preferably receives the in-phase signal andthe quadrature signal from the analog-to-digital converter. Phase dataas a function of range, referenced herein as phase-range data, andamplitude data as a function of range, referenced herein asamplitude-range data, are calculated from the in-phase signal and thequadrature signal. In preferred embodiments, the digital signalprocessor also receives trigger data and azimuth angle data from theradar device. The central processing unit is preferably used to enhancedetection of the target, using phase-range data, as well as trigger dataand azimuth angle data. In some embodiments, the processor also usesamplitude-range data to enhance detection of the target. A display ispreferably used for showing the enhanced detection of the target.

Also disclosed herein is a system for enhanced detection of a target.Embodiments of the preferred system include a computer-readable mediumhaving computer-executable instructions for performing a method. Thepreferred method, referred to as an enhanced detection method, includes:(1) receiving phase-range data for a return pulse associated with atarget; (2) receiving amplitude-range data for the return pulse; and (3)receiving second phase-range data for a second return pulse associatedwith the target. The phase-range data and the second phase-range dataare preferably compared to obtain a change in phase or phase delta,herein referenced as a “difference.” The use of numbering nomenclatureherein, such as “(1)”, “(2)” and “(3)” above, are used for the purposesof clarity and do not require that steps in the method be implemented ina specific order or require that the method lacks intermediate steps.

Continuing with a description of the preferred method, a subset of rangesamples is created from that amplitude-range data which satisfies anamplitude threshold. An amplitude mask is built from the subset and thenis applied to the difference to create what is referenced herein as a“masked difference.” The masked difference is then differentiated withrespect to range to obtain what is herein referenced as a“differentiated masked difference” or a “derivative of the maskeddifference.” The target is preferably detected by identifyingcoordinates of the differentiated masked difference that satisfy avelocity threshold. In preferred embodiments, the enhanced detectionmethod checks the envelope of the amplitude-range data and a target isidentified when detected by the velocity threshold and/or the envelopecheck.

Preferred embodiments of the invention include a computer-readablemedium having stored thereon computer-executable instructions forperforming the following method. The computer-executable instructionsare preferably for providing phase-range data associated with a returnpulse of a radar device and second phase-range data associated with asuccessive return pulse of the radar device. In some aspects, providingphase-range data and second phase-range data includes providing an arrayof phase data as a function of range data and a second array of secondphase data as a function of second range data. The return pulse may beassociated with one of a plurality of radar devices. Preferredembodiments of the computer-readable medium include computer-executableinstructions for extracting the phase-range data and second phase-rangedata from an in-phase signal and a quadrature signal taken from anintermediate frequency signal of a radar device.

The computer-executable instructions are preferably also fordiscriminating a target from clutter by using the differentiateddifference to identify coordinates satisfying a velocity thresholdassociated with the clutter. In some embodiments, said discriminatingmay include discriminating the target from the clutter by using thedifferentiated difference to identify coordinates associated with avelocity exceeding clutter velocity. In some embodiments, saiddiscriminating includes identifying clutter behavior and filtering-outcoordinates of the differentiated difference associated with the clutterbehavior. Identifying clutter behavior preferably includes identifyingan anomalous change of velocity and/or identifying an anomalous changeof amplitude. In some embodiments of the invention, an anomaly, such asan anomalous change of velocity, is determined within the bounds ofstatistical observations typical of the prevailing clutter scene. Thefiltering-out process preferably includes identifying a contact withconsistent velocity that persists for a period of time exceeding themaximum duration of typical clutter events with similar velocity andfiltering-out other contacts.

Preferred embodiments of the invention include a computer-readablemedium having stored thereon computer-executable instructions forperforming the following method: (1) providing phase-range dataassociated with a return pulse of a radar device, second phase-rangedata associated with a successive return pulse of the radar device, andamplitude-range data associated with at least one of the return pulseand the successive return pulse; (2) comparing the phase-range data andthe second phase-range data to obtain a difference; (3) creating asubset of coordinates from the amplitude-range data that satisfy anamplitude threshold associated with the clutter; (4) building anamplitude mask from the subset; (5) applying the amplitude mask to thedifference; (6) differentiating the masked difference; and (7)discriminating a target from clutter by identifying coordinates from thedifferentiated masked difference satisfying a velocity thresholdassociated with the clutter.

Preferred embodiments of the invention include a system fordiscrimination of a target from clutter. The system preferably comprisesa computer-readable medium having stored thereon computer-executableinstructions for performing a method and at least one computing devicefor executing the computer-executable instructions stored on thecomputer-readable medium. Suitable computing devices are known in theart and may include the central processing unit.

Some embodiments of the system include means for non-invasivelyacquiring an intermediate frequency signal of the radar device and meansfor downconversion of the intermediate frequency signal to an in-phasesignal and a quadrature signal. Preferred embodiments of the means fornon-invasively acquiring the intermediate frequency signal include an IFdata line for non-invasively tapping a radar device. Preferredembodiments of the means for downconversion include a coherentoscillator for generating a coherent oscillator signal and a mixer formixing the intermediate frequency signal and the coherent oscillatorsignal.

Some embodiments of the system include the radar device, which ispreferably a non-coherent radar device. Some embodiments of the systeminclude a display for showing the discriminated target substantiallyfree of clutter. The target preferably includes at least a portion of awatercraft and may include a submarine periscope. In some embodiments ofthe system, the target comprises a human, a land vehicle, or both. Theclutter preferably comprises at least one of terrain clutter, rainclutter, and discrete clutter, and more preferably comprises seaclutter. Some embodiments of the system are substantially free of acoherent radar device.

Embodiments of the present invention include a method for discriminationof a target from clutter. The method for discrimination of a target fromclutter preferably includes providing phase-range data associated with areturn pulse of a radar device, second phase-range data associated witha successive return pulse of the radar device, and amplitude-range dataassociated with at least one of the return pulse and the successivereturn pulse. The method preferably also includes: (1) comparing thephase-range data and the second phase-range data to obtain a difference;(2) creating a subset of coordinates from the amplitude-range data thatsatisfy an amplitude threshold associated with the clutter; (3) buildingan amplitude mask from the subset; (4) applying the amplitude mask tothe difference; (5) differentiating the masked difference; and (6)discriminating the target from the clutter by identifying coordinatesfrom the differentiated masked difference satisfying a velocitythreshold associated with the clutter.

The method for discrimination of a target from clutter preferably alsoincludes deriving the phase-range data, the second phase-range data andthe amplitude-range data from an in-phase signal and a quadrature signalassociated with an intermediate frequency signal of a radar device. Insome aspects, the method includes downconverting the intermediatefrequency signal with a coherent oscillator signal to produce thein-phase signal and the quadrature signal. Downconverting preferablyincludes downconverting to produce the in-phase signal and quadraturesignal in an analog format for conversion into a digital format.

In some embodiments of the method for discrimination of a target fromclutter, the method includes non-invasively acquiring the intermediatefrequency signal from the radar device, preferably a non-coherent radardevice. In some aspects, the method includes extracting the phase-rangedata, second phase-range data and amplitude-range data from the in-phasesignal and quadrature signal. Some embodiments of the method includeshowing the discriminated target substantially free of clutter.

In preferred embodiments of the method, discrimination includes usingthe differentiated masked difference to identify coordinates associatedwith a velocity exceeding clutter velocity. In some aspects of theinvention, discrimination includes: (1) identifying clutter behavior;and (2) filtering-out coordinates of the differentiated mask differenceassociated with the clutter behavior. The identification of clutterbehavior preferably includes identifying an anomalous change of velocityand/or an anomalous change of amplitude. In some embodiments of theinvention, an anomaly, such as an anomalous change of velocity, isdetermined within the bounds of statistical observations typical of theprevailing clutter scene. Identifying coordinates unassociated withclutter behavior preferably includes identifying a contact withconsistent velocity that persists for a period of time exceeding themaximum duration of typical clutter events with similar velocity.

Preferred embodiments of the invention also include a method fordiscrimination of a target from clutter using an intermediate frequencysignal of a non-coherent radar device. The method preferably includes:(1) acquiring the intermediate frequency signal from the non-coherentradar device; (2) manipulating the intermediate frequency signal toprovide phase-range data associated with a return pulse of thenon-coherent radar device and second phase-range data associated with asuccessive return pulse of the non-coherent radar device; and (3)comparing the phase-range data and the second phase-range data to obtaina difference.

The method for discrimination of a target from clutter using theintermediate frequency signal of the non-coherent radar devicepreferably further includes identifying at least one disturbance in aslope of the difference satisfying a threshold, and identification mayinclude the use of a linear regression technique and/or a wavelettransform. Preferred embodiments of the method for discrimination of atarget from clutter using the intermediate frequency signal of thenon-coherent radar device also include differentiating the differenceand identifying at least one disturbance in a slope of thedifferentiated difference satisfying a velocity threshold. Theintermediate frequency signal is preferably also manipulated to provideamplitude-range data associated with at least one of the return pulseand the successive return pulse.

Additional embodiments of the method for discrimination of a target fromclutter using the intermediate frequency signal of the non-coherentradar device include: (1) building an amplitude mask from at least aportion of the amplitude-range data; (2) applying the amplitude mask tothe difference; (3) differentiating the masked difference; and (4)identifying at least one disturbance in a slope of the differentiatedmasked difference satisfying a velocity threshold. In some embodiments,the method includes showing coordinates of the at least one disturbancein the slope that satisfy the velocity threshold. In some embodiments,the method includes creating a subset of coordinates from theamplitude-range data that satisfy an amplitude threshold. The amplitudemask is preferably built from the subset.

Preferred embodiments of the invention also include a radar systemhaving a radar device that comprises a non-coherent transmitter sectionfor generating and transmitting first and second pulsed RF oscillatorysignals, and a receiver section for detecting first and second returnsignals. The radar system preferably also includes: (1) means foracquiring an intermediate frequency signal from the radar device, suchas an IF data line connected to a suitable tap point of the radardevice; (2) means for downconverting the intermediate frequency signalto produce an in-phase signal in an analog format and quadrature signalin an analog format, such as a mixer and coherent oscillator; (3) meansfor converting the analog format of the in-phase signal and the analogformat of the quadrature signal into digital formats, such as an A-Dconverter; and (4) means for using the in-phase signal and quadraturesignal to discriminate a target from clutter by identifying adisturbance in a phase difference between phase-range data associatedwith the first return signal and second phase-range data associated withthe second return signal, such as the digital signal processor and thecentral processing unit. Preferred embodiments of the radar systeminclude a means for showing the discriminated target. In some aspects,the radar device may be used to show the discriminated target. Someembodiments of the radar system are substantially free of a coherentradar device.

Preferred embodiments of the invention include a method for substantialremoval of relative phase variations from a radar device with anon-coherent transmitter section. The method preferably includes: (1)non-invasively acquiring an intermediate frequency signal from the radardevice; (2) downconverting the intermediate frequency signal with acoherent oscillator signal to produce an in-phase signal in an analogformat and a quadrature signal in an analog format; (3) converting theanalog format of the in-phase signal and the analog format of thequadrature signal into digital formats; (4) using the in-phase signaland quadrature signal to provide phase-range data associated with areturn pulse of the radar device, second phase-range data associatedwith a successive return pulse of the radar device, and amplitude-rangedata associated with at least one of the return pulse and the successivereturn pulse; (5) comparing the phase-range data and the secondphase-range data to obtain a difference; (6) creating a subset ofcoordinates from the amplitude-range data that satisfy an amplitudethreshold associated with the clutter; (7) building an amplitude maskfrom the subset; (8) applying the amplitude mask to the difference; and(9) differentiating the masked difference. In preferred embodiments ofthe invention, the differentiated masked difference is is the phasedifference drift rate for the non-coherent transmitter section andreceiver section of the radar device.

Preferred embodiments of the invention also include a method ofnon-invasively cohering a non-coherent radar device. The methodpreferably includes the following: (1) acquiring an intermediatefrequency signal from the non-coherent radar device; (2) manipulatingthe intermediate frequency signal to provide phase-range data associatedwith a return pulse of the non-coherent radar device and secondphase-range data associated with a successive return pulse of thenon-coherent radar device; and (3) comparing the phase-range data andthe second phase-range data to obtain a difference. Manipulatingpreferably includes manipulating the intermediate frequency signal toprovide amplitude-range data associated with at least one of the returnpulse and the successive return pulse. Some embodiments of the methodfurther include differentiating the difference.

The method of non-invasively cohering a non-coherent radar devicepreferably also includes building an amplitude mask from at least aportion of the amplitude-range data and applying the amplitude mask tothe difference. Preferred embodiments of the method preferably includecreating a subset of coordinates from the amplitude-range data thatsatisfy an amplitude threshold, and wherein building comprises buildingthe amplitude mask from the subset. Some embodiments of the method ofnon-invasively cohering a non-coherent radar device includedifferentiating the masked difference.

Preferred embodiments of the invention include an enhanced detectionsystem, including the following: (1) a coherent oscillator forgenerating a coherent oscillator signal; (2) a mixer for mixing thecoherent oscillator signal and an intermediate frequency signal of anon-coherent radar device to downconvert the intermediate frequencysignal to an in-phase signal and a quadrature signal in an analogformat; (3) an analog-to-digital converter for converting the analogformat of the in-phase signal and quadrature signal into a digitalformat; (4) a digital signal processor for using the in-phase signal andquadrature signal in the digital format to provide phase-range data of areturn pulse of the non-coherent radar device and second phase-rangedata of a successive return pulse of the non-coherent radar device; (5)a computing device that compares the phase-range data and the secondphase-range data to obtain a difference, differentiates the difference,and discriminates a target from clutter by using the differentiateddifference to identify coordinates satisfying a velocity thresholdassociated with the clutter; and (6) a display for showing thediscriminated target substantially free of clutter. Some embodiments ofthe enhanced detection system include the non-coherent radar device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate the embodiments of the present inventionand, together with the description serve to explain the principles ofthe invention. In the drawings:

FIG. 1 is a block diagram showing a radar device coupled with apreferred embodiment of an enhanced detection device;

FIG. 2 is a screenshot of a display showing clutter obscuring a target;

FIG. 3 is a screenshot of a display showing enhanced detection of thetarget of FIG. 2;

FIG. 4 is a block diagram showing another preferred embodiment of theenhanced detection device shown in FIG. 1;

FIG. 5 is a block diagram showing another preferred embodiment of theenhanced detection device shown in FIG. 1;

FIG. 6 is a block diagram showing another preferred embodiment of theenhanced detection device shown in FIG. 1;

FIG. 7 is a flow chart showing a preferred embodiment of an enhanceddetection method implemented by the enhanced detection device of FIG. 1;

FIG. 8 is a graph showing a sample embodiment of the relative amplitudesof a pulse, clutter and noise;

FIG. 9 is a graph showing a trace of the phase of a first sample pulsewith respect to range (P1);

FIG. 10 is a graph showing trace P1 shown in FIG. 9 along with a traceof the phase of a second sample pulse with respect to range (P2);

FIG. 11 a is a graph showing a trace of the difference ΔP between the P1trace shown in FIGS. 9 and 10 and the P2 trace shown in FIG. 10;

FIG. 11 b is a display showing a sample trace of a sample difference ΔPbetween a sample P1 trace and a sample P2 trace;

FIG. 12 a is a graph showing a trace of the derivative of the ΔPfunction of FIG. 11 a;

FIG. 12 b is a display showing a sample trace of the derivative of thesample ΔP function of FIG. 11 b;

FIG. 13 is a graph showing the trace of FIG. 12 a with a slopedisturbance representative of a potential target;

FIG. 14 is a graph showing the trace of FIG. 11 a with a slopedisturbance representative of a potential target;

FIG. 15 is a display showing simple application of velocity thresholdstep to a derivative of a ΔP function; and

FIG. 16 is a flow chart showing a preferred embodiment of a velocitythreshold step.

DETAILED DESCRIPTION OF THE INVENTION

In describing a preferred embodiment of the invention illustrated in thedrawings, specific terminology will be used for the sake of clarity.However, the invention is not intended to be limited to the specificterms so selected, and it is to be understood that each specific termincludes all technical equivalents which operate in a similar manner toaccomplish a similar purpose.

With principal reference to FIG. 1, an enhanced detection system isdesignated generally 100 and shown coupled to a radar device 10. Inpreferred embodiments, enhanced detection system 100 comprises a mixer20, a coherent oscillator 30, an analog-to-digital converter 40, adigital signal processor 50, a central processing unit 60, a display 70,and an input device 80.

Enhanced detection system 100 is suitable for cohering non-coherentradar devices, such as a magnetron-based radar device; however,embodiments of enhanced detection system 100 may also be suitable forenhancing the performance of radar devices already having high levels ofcoherence. Radar device 10 preferably comprises a navigation orsurveillance radar device that is interfaced to enhanced detectionsystem 100 via an IF data line 15, a trigger data line 13, and anazimuth angle data line 17. IF data line 15 preferably comprises acoaxial RF cable; however, any suitable signal medium can be utilized.IF data line 15 passes the intermediate frequency signal from radardevice 10 to mixer 20. In preferred embodiments of enhanced detectionsystem 100, the intermediate frequency signal is non-invasivelyextracted from an appropriate tap point on radar device 10 such thatnormal operation of radar device 10 is undisturbed. The intermediatefrequency signal that is passed to IF data line 15 is representative, atleast in part, of target and clutter information received by radardevice 10 on a return pulse.

Mixer 20 is also in electrical communication with coherent oscillator 30to permit downconversion of the intermediate frequency signal. Mixer 20outputs an in-phase signal in an analog format and a quadrature signalin an analog format, which preferably comprise I and Q video signals.These in-phase and quadrature signals are passed along cables or othersignal mediums, herein referenced as analog I-line 23 and analog Q-line27, to analog-to-digital converter 40. The chosen frequency output ofcoherent oscillator 30 is preferably matched with the intermediatefrequency signal and the chosen analog-to-digital converter 40 tooptimize performance. Analog-to-digital converter 40 digitizes theanalog formats of the in-phase signal and quadrature signal.

Known embodiments of coherent radar devices (including fully-coherentradar devices and coherent-on-receive devices) use a signal source, suchas a local oscillator, to serve as the phase reference to establish andmaintain coherence of the return signal. Coherent oscillator 30 ispreferably used for downconversion of the intermediate frequency signalto the in-phase signal and the quadrature signal at a frequency suitablefor conversion by analog-to-digital converter 40. Preferred embodimentsof the invention do not require that coherent oscillator 30 serve as aphase reference.

Preferred systems include a computing device, such as one includingdigital signal processor 50 and central processing unit 60 and acomputer-readable medium. Digital signal processor 50 receives thein-phase signal and quadrature signal from analog-to-digital converter40 via digital I-line 43 and digital Q-line 47. Digital signal processor50 receives azimuth angle data passed via azimuth angle data line 17from radar device 10 and receives trigger data via trigger data line 13from radar device 10. Digital signal processor 50 utilizes the triggerdata for timing and the azimuth angle data for proper showing of thetarget on a display.

Data from digital signal processor 50 is then passed via a signal mediumto a processor, such as central processing unit 60, where targetdetection and discrimination occur. A computer-readable mediumpreferably includes computer-executable instructions stored therein forcentral processing unit 60 or other computing device to implement themethod of the computer-executable instructions. A preferred enhanceddetection method minimizes clutter interference originally present onthe return pulse and sends enhanced target data to display 70 allowingviewing of targets that may have originally been obscured by clutter.The preferred enhanced detection method will be discussed below infurther detail with principal reference to FIG. 7 and FIG. 16.

Continuing with principal reference to FIG. 1, enhanced target data issent to display 70 via a signal medium for substantially clutter-freeviewing of the target. In preferred embodiments, display 70 uses agraphical user interface (GUI). Enhanced detection system 100 alsoincludes at least one input device 80, such as a mouse, keyboard orother suitable input device known in the art. In this respect, inputdevice 80 can be used to control operations of digital signal processor50, central processing unit 60, both, and/or other components.

With principal reference to FIGS. 2 and 3, enhanced detection system 100substantially enhances the accuracy in which the return pulse data isdisplayed. Enhancement detection system 100 removes clutter, revealing aclear target distinguished from clutter. For example, the results oftesting against collected data are shown in FIG. 2, where the sampletarget, a thirty-foot scarab, is obscured by clutter. Thus, although thetarget may be detected by a radar device, such as radar device 10, thesimultaneous display of detected clutter obscures the display of thedetected target. However, as shown in FIG. 3, enhanced detection system100 produces enhanced target data revealing the target, which is nolonger obscured by clutter.

With principal reference to FIGS. 4 through 6, some embodiments ofenhanced detection system 100 comprise fewer or more components than theembodiment shown in FIG. 1. For example, as shown in FIG. 4, enhanceddetection system 100 a is shown to include digital signal processor 50,central processing unit 60, display 70, and input device 80. As shown,enhanced detection system 100 a is coupled to radar device 10, mixer 20,coherent oscillator 30, and analog-to-digital converter 40; however,enhanced detection system 100 a can also be connected directly to aradar device having a digital output that transmits the in-phase signaland quadrature signal or the phase-range data and amplitude-range dataof a return pulse. FIG. 5 shows another embodiment of enhanced detectionsystem 100 b, which comprises digital signal processing unit 50 andcentral processing unit 60.

As another example, FIG. 6 shows another embodiment of enhanceddetection system 100 c, which includes radar device 10, itself being anintegrated component of enhanced detection system 100 c. Notably, whileFIG. 6 shows that radar device 10 is a separate component from display70, radar device 10 may comprise display 70 such that the enhancedtarget data may be shown directly on the screen of radar device 10.Additional embodiments of enhanced detection system 100 are contemplatedand the various components of enhanced detection system 100 may bedistributed in any number and manner of combination. Enhanced detectionsystem 100 may also be linked to a communications network (not shown)for remote review and analysis of all data. It is contemplated thatembodiments of enhancement detection system 100 are operable withvarious commercial embodiments of radar device 10 and are thusinterchangeable between the various embodiments of radar device 10. Inthis respect, enhanced detection system 100 may be characterized asbeing modular.

With principal reference to FIG. 7, a preferred embodiment of theenhanced detection method implemented by enhanced detection system 100is designated generally as 200 and will now be discussed in furtherdetail. Radar device 10 is used more effectively for discriminatingtargets from clutter when enhanced detection method 200 is used. Saidclutter may result from the environment of the target, such as the sea(or other body of water) or the surrounding terrain. Unless indicatedherein to the contrary, the steps and sub-steps of enhanced detectionmethod 200 may be implemented in any logical order. Furthermore, in someembodiments of enhanced detection method 200, multiple steps may occursubstantially simultaneously (e.g. parallel processing). In someembodiments of enhanced detection method 200, steps may share portionsof computer code. Some embodiments of enhanced detection method 200 donot require all of the steps shown in FIG. 7.

At mixing step 205, mixer 20 mixes the intermediate frequency signalfrom radar device 10 and the signal from coherent oscillator 30 tooutput signals carrying amplitude and phase information, whichpreferably include an in-phase signal in analog format and a quadraturesignal in an analog format. At conversion step 210, the analog formatsare digitized by analog-to-digital converter 40 and the in-phase signaland quadrature signals are sent in digital format to digital signalprocessor 50 and central processing unit 60 for discrimination anddetection.

The in-phase signal and the quadrature signal may be converted to aphase signal and an amplitude signal. The process may operate either onthe in-phase signal and the quadrature signal or on the phase signal andthe amplitude signal. However, for the purpose of clarity of disclosure,it is easier to describe the preferred method in terms of a phase signaland an amplitude signal. The phase signal contains phase-range data,referenced herein as PRD, and the phase signal contains PRD associatedwith at least one return pulse P_(i). PRD P_(i) preferably comprises anarray of phase data as a function of range data [r_(i), Φ(r_(i))]associated with the return pulse P_(i). The amplitude signal containsamplitude-range data, referenced herein as ARD, and the amplitude signalcontains ARD preferably associated with the same return pulse P_(i). ARDP_(i) preferably comprises an array of amplitude data as a function ofrange data [r_(i), A(r_(i))] associated with the return pulse P_(i).

The preferred enhanced detection method 200 can be described from theperspective of two branches of an “OR” operation that occurs atidentification step 255. One side of the OR operation of identificationstep 255 preferably includes envelope detection step 215, while theother side of the OR operation occurs between delay step 220 andvelocity threshold step 250, inclusively. The OR operation ofidentification step 255, along with all other suitable steps in thevarious embodiments of enhanced detection method 200, may beaccomplished by using hardwired logic, programmable logic, software, orany combination thereof.

One of the two sides of the OR operation of identification step 255preferably includes envelope detection step 215, which attemptsdetection of the target by using ARD P_(i). Some embodiments of enhanceddetection method 200 include this threshold stage to detect largetargets with standard envelope-detection logic. However,envelope-detection is plagued by an undesirable margin of error,particularly for small targets, because it may be difficult to discernthe target from the clutter and/or noise. A sample quantitativecomparison between these amplitudes is shown in FIG. 8. Forcircumstances where the target could easily be detected by studying theenvelope of the return pulse, envelope detection step 215 acts as aprophylactic measure designed to identify a target that is notidentified, for whatever reason, by the phase-based detection on theother side of the OR logic of identification step 255. Some embodimentsof enhanced detection method 200 do not require envelope detection step215.

Continuing with principal reference to FIG. 7, the other side of the ORoperation of identification step 255 is preferably a phase-baseddetection method that includes delay step 220, comparison step 225,subset step 230, mask building step 235, masking step 240,differentiating step 245, and velocity threshold step 250. Delay step220 and comparison step 225 prepare the phase-based information to bemasked at masking step 240, while subset step 230 and mask building step235 use amplitude-based information to prepare the mask that is appliedat masking step 240.

In preferred embodiments of enhanced detection method 200, delay step220 and comparison step 225 prepare the phase-range data for masking.Delay step 220 uses the phase-range data of the return pulse PRD P_(i)and a trace of PRD P_(i) is shown in FIG. 9 and labeled P1. At delaystep 220, additional phase-range data is obtained, preferably by aone-pulse delay, for the next return pulse P_(i+1). The phase-range dataof the successive pulse is referenced herein as PRD P_(i+1) andpreferably comprises an array of phase data as a function of range data[r_(i+1), Φ(r_(i+1))]. Output of the one-pulse delay includes PRD P_(i)and PRD P_(i+1), each of which preferably include a phase-range array.Traces of PRD P_(i) and PRD P_(i+1) are shown in FIG. 10 and are labeledP1 and P2, respectively.

At comparison step 225, the arrays of PRD P_(i) and PRD P_(i+1) arecompared to yield the change in the phase information between the twoarrays. This difference is referenced herein as PRD ΔP and preferablycomprises an array of change in phase data as a function of range data[r_(i), ΔΦ(r_(i))]. Difference PRD ΔP is then passed to masking step240, which will be further discussed below in detail after discussion ofsubset step 230 and mask building step 235. A trace of difference PRD ΔPis shown in FIG. 11 a and a display is shown in FIG. 11 b to include asample trace of the difference ΔP between a sample P1 trace and a sampleP2 trace. Although sample data rarely produces an ideal or linear trace,suitable methods are known in the art to account for deviations from theideal.

Subset step 230 and mask building step 235 use amplitude-basedinformation to prepare the mask. Subset step 230 uses theamplitude-range data of the return pulse ARD P_(i). At subset step 230,a subset of ARD P_(i) is created that contains coordinates that satisfyan amplitude threshold. In the preferred embodiment, only rangecoordinates for signals of sufficient amplitude are allowed to proceedalong the signal and/or logic path for further processing. In thisrespect, the analysis of the phase-range data is, in preferredembodiments, limited to certain data points that have not been ruled-outas potentially noise limited. At mask building step 235, an amplitudemask is built from the subset created in subset step 230. The amplitudemask is preferably a function of range. Any suitable amplitude maskknown in the art may be used.

Continuing with principal reference to FIG. 7, the amplitude mask isapplied to the difference at masking step 240. The amplitude mask isused, at least in part, to control false alarms for the processedphase-range data. Some embodiments of enhanced detection method 200 donot require subset step 230, mask building step 235 and/or masking step240; however, such steps are present in the preferred embodiment ofenhanced detection method 200.

At differentiating step 245, the masked difference is differentiatedwith respect to range. The derivative is performed, at least in part, toaid in the target detection and discrimination process. An additionalbenefit of the derivative is that it resolves intra-pulse phaseinstabilities, which may be a consequence of oscillator drift inmagnetron-based systems. It is contemplated that some embodiments ofenhanced detection method 200 could use linear regression techniquesand/or wavelet transforms in place of differentiating step 245.

At velocity threshold step 250, enhanced target detection is attemptedby identifying coordinates in the derivative of the masked differencethat satisfy a velocity threshold. Pulse-to-pulse phase difference maybe used to calculate velocity. The derivative of the masked difference,also referenced herein as a “differentiated mask difference,” is ameasure of velocity as a function of range and a trace and sample traceare shown in FIGS. 12 a and 12 b, respectively, with no target present.In contrast thereto, FIG. 13 shows a slope disturbance in thedifferentiated masked difference. In this respect, the velocitythreshold discriminates contacts that have velocity content differingfrom the clutter. As discussed, it is preferred, but not required, thatthe masked difference be differentiated. As shown in FIG. 14, a slopedisturbance representative of a target is shown in a trace of anon-differentiated masked difference. The complexity and/or difficultyof the processing of velocity threshold step 250 are minimized if thedifferentiated masked difference is analyzed rather than thenon-differentiated masked difference. The reduction in complexity may beobserved by comparison of the graphs shown in FIGS. 13 and 14. FIG. 15shows a sample trace that evidences the types of coordinates present ina differentiated masked difference for a simple velocity threshold (thehorizontal trace demonstrates the simple velocity threshold). Velocitythreshold step 250 will be discussed in further detail below withprincipal reference to FIG. 16.

Continuing with principal reference to FIG. 7, identification step 255identifies whether a target has been detected by at least one ofenvelope detection step 215 and the method of steps 220-250. Thispermits identification of a target that satisfies either of envelopedetection step 215 or velocity threshold step 250. When a target isdistinguished due to enhanced detection, then the enhanced target datais displayed at display step 260. At loop step 265, “i” is incrementedand the data on a successive pulse pair is studied (e.g. PRD_((i+1)) andPRD_((i+1)+1)).

Velocity threshold step 250 will now be further discussed with principalreference to FIG. 16. In the event that the potential target is arelatively fast moving target, and particularly when the potentialtarget moves much faster than clutter velocity, the target may bediscriminated from the clutter by a simple comparison of the magnitudeof the instantaneous velocity at a given coordinate against a magnitudethat is equal to, or greater than, a chosen clutter velocity. Thistechnique is particularly effective for detecting fast-moving targets.

However, should the target be a relatively slow-moving target, such aswhen the target moves at a velocity close to or below clutter velocity,then it is not preferable to make a simple comparison between thederivative of the masked difference and a clutter velocity. If, by wayof example, clutter velocity is two knots, then a simple velocitythreshold should suffice for detecting a potential target moving at fourknots. However, in the case of a slow-moving target, such as a periscopemoving at one and one-half knots, it becomes more difficult todiscriminate the target from the clutter using a simple comparison ofthe derivative of the masked difference to a clutter velocity. In such acase, it is desirable to analyze more than a simple comparison of thedifferentiated masked difference to the clutter velocity or a simplecomparison of the differentiated difference to the clutter velocity.This additional analysis and process will now be discussed further.

Clutter may be characterized as having certain clutter behavior.Clutter, such as sea clutter, terrain clutter, etc. has velocitysignatures that may also be affected by external factors, such as radarfrequency and wind conditions. For example, a statistical sampling ofclutter at a given coordinate over time would reveal erratic changes ofvelocity and amplitude readings. These anomalous changes of velocityover time and/or anomalous changes of amplitude over time are preferablyused by velocity threshold step 250 as another measure for filtering outclutter in the discrimination of the target from the clutter.

Continuing with principal reference to FIG. 16, velocity threshold step250 preferably includes simple comparison step 305, target detectionstep 310, information gathering step 315, velocity derivation step 320,velocity analysis step 325, target non-detection step 330 and amplitudeanalysis step 335. At simple comparison step 305, the magnitude of thedifferentiated masked difference passed from differentiating step 245 iscompared against the clutter velocity. In the event that thedifferentiated masked difference—or other value, such as a difference ordifferentiated difference, depending upon the embodiment—is associatedwith a velocity exceeding clutter velocity, then target detection step310 indicates an instance of target detection to identification step255. Note that the “clutter velocity” may be chosen to be the velocityof the clutter or it may be chosen to be a value slightly higher thanthe velocity of the clutter, depending upon the desired embodiment ofthe invention.

At information gathering step 315, PRD and ARD are gathered over time,preferably by obtaining information about successive pulses. At velocityderivation step 320, the additional PRD, and optionally the additionalARD, are used to derive additional velocity information. In preferredembodiments, “i” is incremented through a looping process analogous tothat shown in FIG. 7 and the method of information gathering step 315and velocity derivation step 320 are preferably analogous to the methodperformed by steps 220-245 or any sub-combination of steps 220-245.Those skilled in the art will appreciate that the data collection andanalysis of the sub-steps of velocity threshold step 250 can beaccomplished from the data collection and analysis of other steps shownin FIG. 7. For example, as PRD_(i), PRD_(i+1), . . . , PRD_(n) andARD_(i), ARD_(i+1), . . . , ARD_(n) are collected and compared for usein other steps of FIG. 7, said data can be saved, at least temporarily,for use by information gathering step 315 and velocity derivation step320.

At velocity analysis step 325, velocity information over time is studiedto identify whether a potential target is statistically more likely tobe clutter. For example, some clutter characteristically accelerates anddecelerates over time, thus having a signature with sudden changes invelocity. Target non-detection step 330 filters-out coordinatesassociated with these velocity anomalies as being associated with theclutter. Target non-detection step 330 withholds passing an indicationof target detection to identification step 255.

In the embodiment shown in FIG. 16, the amplitude data is analyzed atamplitude analysis step 335, if a velocity anomaly has not been detectedat velocity analysis step 325. Clutter behavior, in addition toincluding signatures that have characteristically sudden drops invelocity, also includes signatures having characteristically suddendrops in amplitude. Target non-detection step 330 filters-outcoordinates associated with these amplitude anomalies as beingassociated with the clutter. Target non-detection step 330 withholdspassing an indication of target detection to identification step 255.

In the embodiment of velocity threshold 250 shown in FIG. 16, targetdetection step 310 indicates an instance of target detection toidentification step 255 if the given coordinate is not associated withclutter behavior, such as anomalous velocity and/or anomalous amplitude.

Although an embodiment of velocity threshold step 250 is shown in FIG.16 and discussed above to include all of steps 305-335, preferredembodiments of velocity threshold step 250 include any combination ofthe steps thereof. For example, some embodiments of velocity thresholdstep 250 principally utilize simple comparison step 305, while someembodiments of velocity threshold step 250 use most of steps 305-335 butomit velocity analysis step 325 or amplitude analysis step 335. Manyembodiments of velocity threshold step 250 are contemplated that includecombinations and/or sub-combinations of steps 305-335 and/or othersteps. When a particular embodiment is used, may depend upon the type oftarget to be detected and/or the estimated velocity range of the targetto be detected. In the case of detecting a target moving substantiallyfaster than clutter velocity, a preferred embodiment of velocitythreshold 250 might principally use simple comparison step 305 andforego the additional processing of velocity analysis step 325 oramplitude analysis step 335. In particular, amplitude analysis step 335is simply another prophylactic measure for discrimination and may, insome embodiments, be omitted.

In testing certain embodiments of enhanced detection system 100, anauxiliary system was designed to improve the detection capabilities ofcommercial maritime radars (e.g. non-coherent, magnetron-based radardevices) for small maritime targets under sea-clutter-limitedconditions. Testing included an embodiment of enhanced detection method200. FIG. 2 shows results of testing against collected data. FIG. 2displays eighty-five scans of data for a clutter-limited scene. Windswere about 10 knots. The x-axis is related to antenna azimuth, withupwind on the right side. FIG. 3 shows that the track of a small target,such as a thirty-foot scarab, is clearly visible after passingphase-range data and amplitude-range data through an embodiment ofenhanced detection system 100.

Tests were conducted using a commercial radar device. Specifically, theradar device used in the testing was a Sperry Bridgemaster E, referencedfurther herein as a Bridgemaster, with a twenty-five kilowatt magnetron.This non-coherent radar device is designed to detect targets usingamplitude-only envelope detection. However, after non-invasive couplingof the Bridgemaster to an embodiment of enhanced detection system 100,positive test results were observed indicating coherence of themagnetron over successive pulses in real-time. In addition to theexpected non-coherence of the magnetron, instabilities in theintra-pulse phase of the intermediate frequency signal of theBridgemaster were also observed. However, test results also indicatedsuccessful real-time stabilization of the intra-pulse phase of theintermediate frequency signal.

Tests were conducted using a digital data recorder that was designed tostart collection based on the trigger of a radar device and record aselectable number of samples at a selectable rate consistent with thepulse width and required range coverage. Using the Bridgemaster, thedigital data recorder demonstrated collection of long-pulse data withtwo megahertz sampling (at two hundred and fifty foot range-gatespacing) and collection of short-pulse data with twenty-one megahertzsampling (at twenty-three foot range resolution). The typical rangecoverage was between about six nautical miles and twelve nautical miles.The digital data recorder was capable of collecting several hours ofdata to a bank of hard drives similar to a redundant array ofindependent disks (RAID).

The radial velocity for each of the backscattered return pulses/echoesfrom each range cell was estimated from the phase difference oversuccessive pulses. The Bridgemaster frequency isnine-thousand-four-hundred-ten (9,410) megahertz and, in long-pulsemode, the Bridgemaster operates at seven-hundred-eighty-five (785) hertzpulse-repetition-frequency (PRF). This provides an ambiguous Doppler of24.3 knots. When a phase difference is calculated for successive pulses,it is substantially equivalent to estimating radial velocity with afifteen degree phase difference per knot. The radial-velocityinformation is useful for discriminating targets from the clutter.

As a nonlimiting example, for conditions typical of sea-state two tothree, the mean sea clutter Doppler velocity for upwind observations ison the order of two knots with most of the radial velocities boundedbetween about zero and four knots. This corresponds to a phasedifference of zero to sixty degrees, where positive phase differencesmay be treated as advancing velocities. Thus, any return pulses withphase differences outside these limits are treated as potential targets,because they behave differently than the ambient clutter. If theshort-pulse mode is used, which operates at one-thousand-eight-hundred(1,800) hertz PRF on the Bridgemaster, there would be an ambiguousDoppler of 55.8 knots. When a phase difference is calculated forsuccessive return pulses, it would be substantially equivalent toestimating radial velocity with a 6.5 degree phase difference per knot.

The Bridgemaster was positioned approximately one-half mile from theshoreline with the antenna at an altitude of approximately sixty (60)feet. Winds were about thirty knots with a solid sea-state of three. Thetarget vessel was a thirty-foot scarab operating from shore out toapproximately four miles. Embodiments of enhanced detection system 100coupled to the Bridgemaster produced and showed enhanced levels oftarget detection on an embodiment of display 70.

In long pulse mode, the amount of time that the antenna of theBridgemaster spent on each radial set of range cells before rotating toan adjacent radial set of range cells was approximately sevenmilliseconds, referenced as the “dwell time.” During the sevenmillisecond dwell time, the Bridgemaster transmitted between four andfive pulses at the approximate rate of 1.3 milliseconds per pulse. Thisprovided approximately four to five opportunities to estimate radialvelocity for each range sample. An M-of-N processing approach wasemployed for amplitude and phase returns within a dwell to control falsealarms. In the tested embodiment of enhanced detection system 100, anyreturns outside the clutter radial-velocity range are preferably passedas potential targets. In preferred embodiments of enhanced detectionsystem 100, performance improvement over standard envelope-detectionprocessors can be achieved by allowing target identification as low asor even lower than a mean level of clutter amplitude.

It is contemplated that embodiments of enhanced detection system 100 mayalso be used to evaluate potential target radial-velocity estimateswithin a dwell as part of the target-identification process. Consistentvelocity estimates within a dwell result in high-confidence targetidentifications, while association of potential targets with radialvelocities consistent over two or more scans results in total-confidenceidentifications. It is contemplated that automatically-detected targetsmay be tagged with radial-velocity estimates after a single dwell.

It is also contemplated that short-pulse modes may be utilized forcommercial and military radar systems to detect small targets, such assubmarine periscopes. Short-pulse operation provides lower average radarsea clutter return, so on average, targets associated with lower radarcross sections should be detectable. Short-pulse sea clutter data takeson characteristics associated with spiky clutter and the sea clutterspikes associated with the wave crests behave like discrete targetsconcentrated in individual range cells. Radar range cells unoccupied bysea spikes contain predominantly receiver noise. Within these rangecells, contemplated embodiments of enhanced detection system 100 mayachieve considerable sub-clutter visibility and make confident targetdeclarations below mean levels of sea clutter amplitude.

In long-pulse mode, the illuminated sea-surface area is large enough topermit multiple sea spikes to exist within a radar range sample. Thisgives rise to the notion that the clutter levels may be treated as beingdistributed. Interference between these multiple discrete scatterers maydegrade the radial velocity estimate. However, in short-pulse mode, thereduced illumination area of the sea surface for each sample tendstoward radar range cells that contain an individual sea-spikephenomenon, and radial-velocity estimation is based on a purer tone,corresponding to the phasor rotation, or Doppler, from an individual,discrete, scattering event, such as a wave crest.

Preferred embodiments of enhanced detection method 200 take advantage ofthe coherent behavior of backscatter from natural clutter phenomena inorder to enhance detection of a target in clutter when using anon-coherent radar device. The phase delta ΔΦ(r_(i)) from pairs ofconsecutive, non-coherent radar pulses contains radial velocityinformation for a target and for a statistically significant number ofclutter elements lying along the target's radial. The radial-velocityinformation from the target can yield a detection when distinguishablefrom that of the clutter elements.

In preferred embodiments of enhanced detection method 200, the radialvelocity information from a non-coherent radar device is corrected forphase instabilities from pulse-to-pulse and within a single pulse.Preferred embodiments of enhanced detection system 100 establishcoherence using a coherent oscillator 30 that is independent of radardevice 10. Preferred embodiments of coherent oscillator 30 are usedprimarily for downconversion of the intermediate frequency signal ofradar device 10. Further, preferred embodiments of enhanced detectionsystem 100 do not require that signals be sent to radar device 10 orthat hardware be invasively installed therein in order for enhanceddetection system 100 to establish coherence. Preferred embodiments ofenhanced detection system 100 use clutter to establish coherence basedon the backscattered return from range cells under surveillance.

1. A computer-readable medium having stored thereon computer-executableinstructions for performing the following method: providing phase-rangedata associated with a return pulse of a radar device and secondphase-range data associated with a successive return pulse of the radardevice; comparing the phase-range data and the second phase-range datato obtain a difference; differentiating the difference; anddiscriminating a target from clutter by using the differentiateddifference to identify coordinates satisfying a velocity thresholdassociated with the clutter.
 2. The computer-readable medium of claim 1,wherein providing phase-range data and second phase-range data comprisesproviding an array of phase data as a function of range data and asecond array of second phase data as a function of second range data. 3.The computer-readable medium of claim 1, wherein discriminatingcomprises discriminating the target from the clutter by using thedifferentiated difference to identify coordinates associated with avelocity exceeding clutter velocity.
 4. The computer-readable medium ofclaim 1, wherein discriminating comprises: identifying clutter behavior;and filtering-out coordinates of the differentiated differenceassociated with the clutter behavior.
 5. The computer-readable medium ofclaim 4, wherein identifying clutter behavior comprises at least one ofidentifying an anomalous change of velocity and identifying an anomalouschange of amplitude.
 6. The computer-readable medium of claim 1, whereinproviding comprises providing phase-range data associated with a returnpulse of one of a plurality of radar devices and second phase-range dataassociated with a successive return pulse of the one of the plurality ofradar devices.
 7. The computer-readable medium of claim 1, furthercomprising computer-executable instructions for extracting thephase-range data and second phase-range data from an in-phase signal anda quadrature signal taken from an intermediate frequency signal of aradar device.
 8. A computer-readable medium having stored thereoncomputer-executable instructions for performing the following method:providing phase-range data associated with a return pulse of a radardevice, second phase-range data associated with a successive returnpulse of the radar device, and amplitude-range data associated with atleast one of the return pulse and the successive return pulse; comparingthe phase-range data and the second phase-range data to obtain adifference; creating a subset of coordinates from the amplitude-rangedata that satisfy an amplitude threshold associated with the clutter;building an amplitude mask from the subset; applying the amplitude maskto the difference; differentiating the masked difference; anddiscriminating a target from clutter by identifying coordinates from thedifferentiated masked difference satisfying a velocity thresholdassociated with the clutter.
 9. The computer-readable medium of claim 8,wherein discriminating comprises discriminating the target from theclutter by using the differentiated difference to identify coordinatesassociated with a velocity exceeding clutter velocity.
 10. Thecomputer-readable medium of claim 8, wherein discriminating comprises:identifying clutter behavior; and filtering-out coordinates of thedifferentiated masked difference associated with the clutter behavior.11. The computer-readable medium of claim 10, wherein identifyingclutter behavior comprises at least one of identifying an anomalouschange of velocity and identifying an anomalous change of amplitude. 12.A system for discrimination of a target from clutter, the systemcomprising: a computer-readable medium having stored thereoncomputer-executable instructions for performing the following method:providing phase-range data associated with a return pulse of a radardevice and second phase-range data associated with a successive returnpulse of the radar device; comparing the phase-range data and the secondphase-range data to obtain a difference; differentiating the difference;and discriminating the target from the clutter by using thedifferentiated difference to identify coordinates satisfying a velocitythreshold associated with the clutter; and at least one computing devicefor executing the computer-executable instructions stored on thecomputer-readable medium.
 13. The system of claim 12, wherein the atleast one computing device comprises at least one processor and an atleast temporary memory.
 14. The system of claim 12, further comprising:means for non-invasively acquiring an intermediate frequency signal ofthe radar device; and means for downconversion of the intermediatefrequency signal to an in-phase signal and a quadrature signalassociated with the phase-range data and the second phase-range data.15. The system of claim 14, wherein the means for downconversioncomprises: a coherent oscillator for generating a coherent oscillatorsignal; and a mixer for mixing the intermediate frequency signal and thecoherent oscillator signal.
 16. The system of claim 14, wherein thesystem is substantially free of a coherent radar device.
 17. The systemof claim 14, further comprising the radar device, and wherein the radardevice is in electrical communication with the means for downconversion.18. The system of claim 17, wherein the radar device comprises anon-coherent radar device in electrical communication with the means fordownconversion.
 19. The system of claim 14, comprising a display forshowing the discriminated target substantially free of clutter.
 20. Thesystem of claim 19, wherein the system is substantially free of acoherent radar device.
 21. The system of claim 12, wherein the targetcomprises at least a portion of a watercraft.
 22. The system of claim12, wherein the target comprises a submarine periscope.
 23. The systemof claim 12, wherein the target comprises at least one of a human and aland vehicle.
 24. The system of claim 12, wherein the clutter comprisessea clutter.
 25. The system of claim 12, wherein the clutter comprisesat least one of terrain clutter, rain clutter, and discrete clutter. 26.A method for discrimination of a target from clutter, comprising:providing phase-range data associated with a return pulse of a radardevice, second phase-range data associated with a successive returnpulse of the radar device, and amplitude-range data associated with atleast one of the return pulse and the successive return pulse; comparingthe phase-range data and the second phase-range data to obtain adifference; creating a subset of coordinates from the amplitude-rangedata that satisfy an amplitude threshold associated with the clutter;building an amplitude mask from the subset; applying the amplitude maskto the difference; differentiating the masked difference; anddiscriminating the target from the clutter by identifying coordinatesfrom the differentiated masked difference satisfying a velocitythreshold associated with the clutter.
 27. The method of claim 26,further comprising deriving the phase-range data, the second phase-rangedata and the amplitude-range data from an in-phase signal and aquadrature signal associated with an intermediate frequency signal ofthe radar device.
 28. The method of claim 27, further comprisingdownconverting the intermediate frequency signal with a coherentoscillator signal to produce the in-phase signal and the quadraturesignal.
 29. The method of claim 28, wherein downconverting comprisesdownconverting to produce the in-phase signal and the quadrature signalin an analog format, and wherein the method further comprises convertingthe in-phase signal and the quadrature signal from the an analog formatinto a digital format.
 30. The method of claim 28, further comprisingnon-invasively acquiring the intermediate frequency signal from theradar device.
 31. The method of claim 30, wherein non-invasivelyacquiring comprises non-invasively acquiring the intermediate frequencysignal from a non-coherent radar device.
 32. The method of claim 26,further comprising displaying the discriminated target substantiallyfree of clutter.
 33. The method of claim 26, wherein discriminatingcomprises discriminating the target from the clutter by using thedifferentiated masked difference to identify coordinates associated witha velocity exceeding clutter velocity.
 34. The method claim 26, whereindiscriminating comprises: identifying clutter behavior; andfiltering-out coordinates of the differentiated masked differenceassociated with the clutter behavior.
 35. The method of claim 34,wherein identifying clutter behavior comprises at least one ofidentifying an anomalous change of velocity and identifying an anomalouschange of amplitude.
 36. A method for discrimination of a target fromclutter using an intermediate frequency signal of a non-coherent radardevice, comprising: acquiring the intermediate frequency signal from thenon-coherent radar device; manipulating the intermediate frequencysignal to provide phase-range data associated with a return pulse of thenon-coherent radar device and second phase-range data associated with asuccessive return pulse of the non-coherent radar device; comparing thephase-range data and the second phase-range data to obtain a difference;differentiating the difference; and identifying at least one disturbancein a slope of the differentiated difference satisfying a velocitythreshold.
 37. A method for discrimination of a target from clutterusing an intermediate frequency signal of a non-coherent radar device,comprising: acquiring the intermediate frequency signal from thenon-coherent radar device; manipulating the intermediate frequencysignal to provide phase-range data associated with a return pulse of thenon-coherent radar device and second phase-range data associated with asuccessive return pulse of the non-coherent radar device; comparing thephase-range data and the second phase-range data to obtain a difference;manipulating the intermediate frequency signal to provideamplitude-range data associated with at least one of the return pulseand the successive return pulse; building an amplitude mask from atleast a portion of the amplitude-range data; applying the amplitude maskto the difference; differentiating the masked difference; andidentifying at least one disturbance in a slope of the differentiatedmasked difference satisfying a velocity threshold.
 38. The method ofclaim 37, further comprising displaying coordinates of the at least onedisturbance in the slope that satisfy the velocity threshold.
 39. Themethod of claim 37, further comprising creating a subset of coordinatesfrom the amplitude-range data that satisfy an amplitude threshold, andwherein building comprises building the amplitude mask from the subset.40. A method for substantial removal of relative phase variations from anon-coherent radar device to discriminate a target from clutter,comprising: non-invasively acquiring an intermediate frequency signalfrom the radar device; downconverting the intermediate frequency signalwith a coherent oscillator signal to produce an in-phase signal havingan analog format and quadrature signal having an analog format;converting the analog format of the in-phase signal and quadraturesignal into a digital format; using the in-phase signal and quadraturesignal to provide phase-range data associated with a return pulse of theradar device, second phase-range data associated with a successivereturn pulse of the radar device, and amplitude-range data associatedwith at least one of the return pulse and the successive return pulse;comparing the phase-range data and the second phase-range data to obtaina difference; creating a subset of coordinates from the amplitude-rangedata that satisfy an amplitude threshold associated with the clutter;building an amplitude mask from the subset; applying the amplitude maskto the difference; differentiating the masked difference; anddiscriminating the target from the clutter by identifying coordinatesfrom the differentiated masked difference satisfying a velocitythreshold associated with the clutter.
 41. A method of non-invasivelycohering a non-coherent radar device, comprising: acquiring anintermediate frequency signal from the non-coherent radar device;manipulating the intermediate frequency signal to provide phase-rangedata associated with a return pulse of the non-coherent radar device andsecond phase-range data associated with a successive return pulse of thenon-coherent radar device; manipulating the intermediate frequencysignal to provide amplitude-range data associated with at least one ofthe return pulse and the successive return pulse; comparing thephase-range data and the second phase-range data to obtain a difference:building an amplitude mask from at least a portion of theamplitude-range data; applying the amplitude mask to the difference toobtain a masked difference; and differentiating the masked difference.42. The method of claim 41, further comprising creating a subset ofcoordinates from the amplitude-range data that satisfy an amplitudethreshold, and wherein building comprises building the amplitude maskfrom the subset.
 43. A method of non-invasively cohering a non-coherentradar device, comprising: acquiring an intermediate frequency signalfrom the non-coherent radar device; manipulating the intermediatefrequency signal to provide phase-range data associated with a returnpulse of the non-coherent radar device and second phase-range dataassociated with a successive return pulse of the non-coherent radardevice; comparing the phase-range data and the second phase-range datato obtain a difference; and differentiating the difference.
 44. Anenhanced detection system, comprising: a coherent oscillator forgenerating a coherent oscillator signal; a mixer for mixing the coherentoscillator signal and an intermediate frequency signal of a non-coherentradar device to downconvert the intermediate frequency signal to anin-phase signal and a quadrature signal in an analog format; ananalog-to-digital converter for converting the analog format of thein-phase signal and quadrature signal into a digital format; a digitalsignal processor for receiving the in-phase signal and quadrature signalin the digital format and providing phase-range data of a return pulseof the non-coherent radar device and second phase-range data of asuccessive return pulse of the non-coherent radar device; a computingdevice for comparing the phase-range data and the second phase-rangedata to obtain a difference, differentiating the difference, anddiscriminating a target from clutter by using the differentiateddifference to identify coordinates satisfying a velocity thresholdassociated with the clutter; and a display for showing the discriminatedtarget substantially free of clutter.
 45. The system of claim 44,further comprising the non-coherent radar device.